GB2620081A

GB2620081A - 3/2-way valve concept for a hydraulic actuation system

Info

Publication number: GB2620081A
Application number: GB2315650.8A
Authority: GB
Inventors: Leiber Heinz; Von Zanten Anton
Original assignee: Ipgate AG
Current assignee: Ipgate AG
Priority date: 2021-04-07
Filing date: 2022-01-28
Publication date: 2023-12-27
Also published as: US20240190405A1; GB202315650D0; JP2024515063A; CN117279811A; DE202021105880U1; EP4320017A1; WO2022214226A1

Abstract

The invention relates to a hydraulic actuation system for a hydraulic system, in particular in the form of a brake system, having the following: - at least one hydraulic circuit (BK) comprising at least one hydraulic load, in particular in the form of a hydraulically actuated wheel brake, - at least one pressure generating device (DV) which has a pump, in particular in the form of a piston pump, and which is used to control or regulate pressure, in particular for building up or relieving pressure (pauf, pab), in the at least one hydraulic circuit (BK1, BK2). The invention is characterized in that the pressure generating device (DV) can be selectively connected to a storage container (VB) or decoupled therefrom by means of at least one controlled 3/2-way valve (PD1, PD2).

Description

3/2 directional control valve concept for hydraulic actuation system The present invention relates to a hydraulic actuation system for a hydraulic system, in particular in the form of a brake system, having at least one hydraulic circuit which is provided with at least one hydraulic consumer, in particular in the form of a hydraulically actuated wheel brake, and having at least one pressure generating device with a piston pump or a rotary pump for pressure control or regulation, in particular for pressure build-up and pressure reduction in the at least one hydraulic circuit.

Such hydraulic actuation systems are sufficiently well known. In automotive engineering, 3/2 valves find versatile application, as disclosed in DE 10 2017000472, where a 3/2-way valve is used for selective connection of a brake circuit to the pressure supply or to a tandem master brake cylinder. The use of a 3/2-way valve can advantageously save a valve when only 2/2-way valves have been used previously.

In many valve applications, the safety requirements for a valve failure are high, as they can have an impact on the braking effect and pedal characteristics.

Task of the invention It is the task of the present invention to design a generic hydraulic actuation system, in particular for a braking system, in a more fail-safe and cost-effective manner.

This task is solved according to the invention with a hydraulic actuating system having the features of claim 1. Further advantageous embodiments of the actuation system according to claim 1 result from the features of the subclaims.

With the actuation system according to the invention, the pressure can advantageously be regulated or controlled very precisely. -2 -

The pressure generating device can advantageously comprise a piston pump. In automotive engineering, there is a wide range of applications for the actuation systems according to the invention. Compared to rotary pumps, electric motor-driven piston-cylinder systems with plunger or double-stroke pistons offer great advantages in continuous medium delivery or also in controlled volume delivery by means of piston displacement measurement or pressure measurement, in which, for example, a very specific volume of hydraulic medium is adjusted by controlled or regulated adjustment of the piston, whereby, for example, a preset pressure can be set or regulated on the basis of a pressure-volume characteristic curve.

However, it is particularly advantageous if the pressure-generating device has a double-stroke piston, so that hydraulic medium can be conveyed in the forward stroke and in the return stroke, and that each working chamber of the pressure-generating device can be connected to the reservoir via a 3/2-way valve, in particular one assigned to it. With this valve circuit described above, for example, any of the currently required functions of a braking system can be realized or set with the piston. For example, it is also possible to adjust the double-stroke piston of the pressure generating device without delivering hydraulic medium, which is generally referred to as an idle stroke without volume delivery into or out of the hydraulic circuits or brake circuits.

However, it is also possible to use a double-stroke piston pump with a 3/2-way valve assigned to only one working chamber or brake circuit and only a 2/2-way valve assigned to the other. In this arrangement, it is then only possible to connect one brake circuit to the reservoir in order to drain hydraulic medium into it or to receive hydraulic medium from it.

In another possible embodiment, the two working chambers of the pressure-generating device can be connected to the reservoir via a single 3/2-way valve, in which case at least one working chamber is always hydraulically connected to the reservoir. As long as the 3/2-way valve can be held in an intermediate position by means of the electromagnetic drive, it is also possible for both working chambers of the piston-cylinder unit of the pressure- -3 -generating device to be hydraulically connected to the reservoir at the same time.

If the hydraulic actuation system with double-stroke pistons according to the invention is used for pressure control of a brake system, it can deliver the hydraulic medium to both brake circuits in the forward stroke as well as in the return stroke. In the event of a failure of one brake circuit (circuit failure), the advantageous valve circuit can continue to control the pressure in the other still intact brake circuit by means of the actuation system.

The brake system can advantageously have a master brake cylinder that is designed either as a tandem or single master brake cylinder. The master cylinder thus has at least one working chamber which can be connected via a 3/2-way valve either in the return plane to a brake circuit or, in the normal case, to a travel simulator for setting a pedal feel. If the master brake cylinder is designed as a tandem master brake cylinder with two working chambers, one of its working chambers can be connected to the brake circuit and travel simulator via a 3/2 directional control valve as described above and the other working chamber can be disconnected from the other brake circuit or connected to it in the return plane by means of a 2/2 directional control valve.

As already described, the pressure supply with so-called dual-circuit double-stroke piston (DHK) enables continuous volume conveyance. With the valve circuit according to the invention, the alternating single-circuit double-stroke piston can distribute the volume to the two brake circuits by piston advance and piston return. At the same time, a pressure equalization between the two brake circuits can take place via a circuit separating valve connecting the two brake circuits in its open position.

The double-stroke piston can advantageously have two differently sized effective areas in the piston forward stroke and piston return stroke. As a rule, the effective piston area in the piston return stroke is only 50')/0 of the effective piston area in the piston advance stroke, with the advantage that the piston force and thus motor torque, e.g. via a spindle drive, in the piston return stroke is only 50% of the piston force in the piston advance stroke, with the same pressure on the effective area. This is advantageously used to -4 -achieve twice the maximum pressure, e.g. up to 200 bar, with the same maximum motor torque during the piston return stroke. In the case of the piston advance stroke, on the other hand, only up to 100bar can be achieved. This fulfills the main requirement that pressure buildup and release is possible over the entire pressure range from 0 -200bar with precise pressure control by piston advance and piston return stroke at any position of the piston.

With the valve circuit according to the invention, the double-stroke piston can advantageously be used for about twenty different operations, if these are to be carried out without compromising dynamics and positioning accuracy. In contrast to the complex valve circuits known from DE 10 20110830312 or DE 10 2018221783, the valve circuit of the hydraulic actuation system according to the invention is significantly simpler, less expensive and smaller.

Even in the event of failure of one hydraulic circuit, the other circuit in the actuation system according to the invention is still ready for use. By providing a redundant motor winding, a higher reliability of the actuator is also achieved. The valve circuit according to the invention can also be used flexibly, so it can also be used for a wide variety of requirements of the hydraulic unit for ABS, ESP and other assistance functions.

To increase safety, a safety shut-off valve, in particular one that is de-energized, can also be arranged in the connecting line that connects the pressure supply to the reservoir and in which a 3/2-way valve is arranged, which disconnects the hydraulic connection between the reservoir and the 3/2-way valve, in particular in the event of malfunction and/or leakage of the 3/2-way valve. This means that even if the 3/2-way valve is leaking, the pressure in at least one wheel brake can still be built up or changed by closing the additional safety shut-off valve by means of the pressure supply.

In the following, the hydraulic actuation system according to the invention and its mode of operation are explained in more detail with the aid of drawings.

They show: -5 -Fig. 1: A possible embodiment of the hydraulic actuation system for supplying pressure to a brake system; Fig. la: Sectional enlargement of the pressure generation device Fig. lb: Enlarged section of the pressure-generating device with only one 3/2-way valve; Fig. 2a and 2b: Schematic illustrations of the 3/2-way valve according to the invention in the de-energized (Fig. 2a) and energized (Fig. 2b) state; Fig. 6: schematic representation of the actuation system according to Fig. la; schematic representation of the actuation system according to Fig. la during pressure build-up in the piston pre-stroke; schematic representation of the actuation system according to Fig. la during pressure reduction in the piston return stroke; Second possible embodiment of the hydraulic actuation system according to the invention with only one 3/2-way valve, whereby one working chamber of the pressure generating device is always in hydraulic connection with the reservoir; Fig. 3: Fig. 4: Fig. 5: Fig. 7: Schematic representation of the actuation system according to Fig. 6; Fig. 8: Use of the actuation system according to Fig. 6 in a brake system with a master brake cylinder; Fig. 9: Cross-section through a possible embodiment of the 3/2-W control valve according to the invention. -6 -

Figure 1 shows a system with master brake cylinder HZ, e.g. single master brake cylinder SHZ with one working chamber R1 or tandem master brake cylinder THZ with two working chambers R1 and R2, together with a reservoir VB and pedal travel sensor 2. In the case of the single master brake cylinder SHZ, a hydraulic line Li leads via a 3/2-way valve MV to the pressure supply DV and to the brake circuit BK1. Via the 3/2-way valve MV, the working chamber R1 is optionally connected via hydraulic line L3 to the travel simulator WS or, in the unpowered normal position, to the brake circuit BK1. The hydraulic line L4 leads directly to the 3/2-way valve PD2 and via the circuit isolating valve KTV to the brake circuit 6K2. The working chamber KV of the pressure generating device DV is connected via the 3/2 directional control valve PD1 either to the second brake circuit BK2 or to the supply reservoir via the return line R. The 3/2-way valves PD1 and PD2 are the main components of the double-stroke piston DHK which are described in detail in Figs. 3-5. The two circuits of the pressure supply DV lead to the hydraulic unit HCU for ABS, ESP and assistance functions, which are supplied with pressure by the pressure supply DV. The pressure generation device can be used not only to build up pressure but also to reduce it.

Figure la shows the actuation system according to Figure 1 alone, with a 3/2-way valve assigned to each working chamber KV, KH. In the return line R to the reservoir VB a normally closed 2/2 shut-off valve MVs is arranged, which is normally open and which becomes effective in case of a failure of the leaky valve seat Se of one of the valves PD1 and PD2. In this case the valve MVs is closed. This is the case when leakage flow occurs in the valve PD1 or PD2 in the non-energized state and flows into the return line R. This can be detected, for example, via the additional volume consumption of brake circuit BK2 or BK1 by means of the pV characteristic or via an unintentional pressure change in brake circuit 3K2 or BK1. The MVs valve can, but does not have to be provided.

Figure lb shows an alternative embodiment in which the second 3/2-way valve PD2 is replaced by a 2/2-way valve so that the working chamber KH can no longer be connected to the reservoir VB. -7 -

Figure 2a shows a schematic representation of a possible embodiment of a 3/2 directional control valve MV for the braking system according to the invention. The 3/2 directional control valve MV has an exciter winding 5 arranged around a magnet yoke 6, in which the magnet armature 4 is adjustable in axial direction to the pin 7, 7a. A stop element 4a is arranged at the left end of the magnet armature 4, which abuts against the inner wall of the magnet yoke 6 in the non-energized second switching state of the valve MV shown in Figure 2a. At the right end of the connecting bolt 7, 7a, the first valve closing body VSK1 is arranged, which is firmly connected to the connecting bolt end 7a. The first valve closing body VSK1 acts together with the first valve seat VS1, which can be part of the solenoid yoke 6. The solenoid yoke 6 forms a first valve chamber K1 in the area of the bolt section 7a, which is in communication with the first valve port an AN1 for connection of the brake circuit BK1 via a hydraulic channel.

The 3/2-way valve MV also has a second valve chamber K2 in which the valve spring VF and a second valve closing body VSK2 are arranged. The second valve chamber K2 is connected via a hydraulic channel to the second valve port AN2, to which the path simulator WS is connected. The second valve chamber K2 forms with its left side the second valve seat VS2 of the valve MV, which cooperates with the second valve closing body VSK2. A third valve chamber K3 is arranged between the two valve seats VS1 and V52 and is connected to the third valve connection AN3 for the master cylinder SHZ or THZ. On the side of the first valve closing body VSK1 facing away from the pin 7, 7a, a plunger ST is formed or fastened, the length of which is dimensioned such that it passes through the first valve seat VS1 and the third valve chamber K3 and can act with its free end on the second valve closing body VSK2 in the energized state of the 3/2-way valve MV. In Figure the pressure supply device is connected to the second brake circuit BK2.

Figure 2b shows the "energized" state of the solenoid valve MV, in which the armature is shifted to the right by the magnetic field of the excitation coil, whereby the first valve closing body VSK1 presses to the right and with the plunger ST against the second valve closing body VSK2 and pushes this away from the second valve seat V52 against the spring force of the valve spring -8 -VF, whereby the pressure supply device DV is now connected to the reservoir VB. The hydraulic connection HV1 between the first valve chamber K1 and the third valve chamber K3 is thereby opened, whereby the working chamber of the pressure generating device DV is connected to the reservoir VB and the brake circuit is disconnected.

The dimensioning of the valve spring VF determines the opening pressure in the return plane, e.g. in the event of failure of the first brake circuit or the pressure supply device DZ. Here, the legislator requires that a vehicle deceleration of 0.24g can be generated with a foot force on brake pedal 1 of 500N. By dimensioning the valve spring to 75bar opening pressure in the master cylinder, almost 3 times the deceleration value can be achieved.

The valve spring VF should be dimensioned in such a way that the solenoid armature 4 is reset more safely and the valve closing body VSK is pressed against the first valve seat VS1 in a secure sealing manner.

Fig. 3 shows the connections of the two 3/2-way valves PD1 and PD2 to the double-lift piston DHK. In the de-energized rest position shown, the valve closing bodies VSK11 and VSK21 of both 3/2-way valves PD1 and PD2 are pressed against the respective valve seats VS11 and V521, thus closing the hydraulic connection between ports AN11 and AN13 or AN21 and AN23. When pressure is applied to the brake circuits BK1 and 6K2, the hydraulic medium acting on the valve closing bodies VSK11 and VSK21 exerts an additional force in the closing direction.

The chamber KV acting in the piston advance stroke is connected via the hydraulic line HL2 to the central third valve port AN13 of the first 3/2-way valve PD1, whereas the chamber KH acting in the piston return stroke is connected via the hydraulic line HL1 to the central third valve port AN23 of the second 3/2-way valve PD2.

The respective second valve ports AN12 and AN22 are connected to the brake circuits 3K2 and BK1. The brake circuits BK1 and 3K2 are connected to each 30 other and separated from each other in the energized state by a de-energized circuit isolating valve KTV. To build up and reduce pressure, the DHK double- -9 -stroke piston moves with a forward or return stroke. The pressure acting in the line/valve supports the valve opening at the two valve seats.

The KTV circuit isolating valve is closed in the event of failure of a BK1 or 3K2 brake circuit. To safeguard against a double fault: In the event of failure of a brake circuit BK1 or BK2 and simultaneous failure of the circuit isolating valve KTV, this circuit isolating valve KTV can also be designed redundantly, e.g. by means of a further circuit isolating valve KTVr connected in series.

Fig. 4 shows the arrangement for the pressure buildup function with the double-stroke piston DHK on piston advance. Here, the piston moves upward in the diagram, the volume flow is directed via the energized 3/2-way valve PD1 with open valve seat V522 and closed valve seat V512 into the brake circuit BK2 and via the circuit isolating valve KTV into the brake circuit BK1. During the piston pre-stroke movement, the double-stroke piston draws volume from the reservoir VB via the open valve seat V521 of the valve PD2 and via the suction valve 5V2.

Fig. 5 shows the pressure reduction during the return stroke of the double-stroke piston DHK with the valve seat V512 open. Here again, the pressure compensation between the two brake circuits BK1 and BK2 acts via the circuit separating valve KTV. The back pressure acts on the valve seats V512 and V522 due to the pressure reduction speed. This can be measured and regulated or controlled by the pressure transmitter via the motor torque or via current or pressure.

From this piston position before the double-stroke piston return stroke, the pressure build-up can also be set in the high pressure range up to e.g. 200 bar. Here, the 3/2-way valve PD2 is energized, causing valve seat V521 to close and valve seat V522 to open. This increases the pressure in brake circuit BK1 and, via the circuit isolating valve KTV, also in brake circuit BK2. During the piston return stroke movement, the double-stroke piston draws volume from the reservoir VB via the open valve seat VS1 and via the suction valve SV1 and VS11 of PD1.

-10 -Figure 6 shows another possible embodiment of the actuation system according to the invention, whereby here only a 3/2-way valve PD1 is provided, with which either the first working chamber KV or the second working chamber KH is connected to the reservoir VB via the hydraulic line HL3. The controlled switching valve PD15 is used for selective hydraulic connection of the first hydraulic line HL1 or the second working chamber KH to a first hydraulic circuit BK1. A second controlled switching valve PD25 in turn serves for selective hydraulic connection of the second hydraulic line HL2 or the first working chamber KV to a second hydraulic circuit BK2, wherein in particular the second hydraulic line HL2 is connected to the second hydraulic circuit 6K2 via a fifth hydraulic line HL5, wherein the second controlled switching valve PD25 serves for selective shut-off or opening of the fifth hydraulic line HL5. A third controlled circuit isolating valve KTV can be used to hydraulically connect or isolate both hydraulic circuits BK1, 3K2.

Figure 7 shows the schematic diagram of the circuit shown in Figure 6.

Figure 8 shows the actuation system according to Figures 6 and 7 in use in a brake system with a master brake cylinder, which can be designed as a single master brake cylinder SHZ with only one working chamber R1 or as a tandem master brake cylinder THZ with two working chambers R1 and R2. The connection of the master brake cylinder corresponds essentially to that described in Figure 1.

Figure 9 shows a possible design of the 3/2-way valve. The upper part, consisting of solenoid armature 4, excitation coil 5, solenoid yoke 6, corresponds to the structure of a standard 2/2-way inlet valve for an antilock braking system (ABS). For this reason, no detailed description is given here and only the lower part, which converts the 2/2-way valve into a 3/2-way valve, is described in detail.

The solenoid yoke 6 serves as a guide for the bolt 7, 7a, which is connected to the first valve closing body VSK1. Compared to the standard design of the 2/2-way inlet valve, the pin 7 can be made smaller in diameter, which increases the effective void area. This also allows the installation of a permanent magnet PM in the yoke 6 for force assistance of the return spring VF, as described in Figure 6, in order to achieve smaller power losses. The first valve closing body VSK1 acts together with the first valve seat VS1 and is hemispherical in shape to achieve or ensure a secure sealing effect. The first valve seat VS 1 is arranged in the solenoid yoke 6. However, the first valve seat VS1 can also be integrated in the magnet yoke 6 or implemented via a flanged plate. A plunger ST is formed on the first valve closing body VSK1 or else connected to the bolt 7a. The plunger engages through the first valve seat VS1 and acts on the second valve closing body VSK2, which is formed as a ball and cooperates with the second valve seat VS2.

As shown, the second valve seat VS2 can be combined with the ball VSK2 and the valve spring VF in a separate housing as a unit. This offers advantages in pre-assembly and valve adjustment. For this purpose, the assembly unit is pressed into the yoke housing. To measure the tappet stroke, the ball stop has a hole to record the path of the ball via a measuring pin. For a secure connection of the assembly unit to the solenoid yoke, a power supply is recommended. To protect the valve seats VS1 and VS2, all connections to the brake circuit, master cylinder and travel simulator are protected by Fl, F2 and F3 filters.

The valve adjustment is made in such a way that the tappet ST has a small distance to the ball VSK2.

To reduce coil heating, the excitation winding 5 can be potted with the solenoid housing 9. In addition, a ribbed heat sink 10 may also be provided.

-12 -List of reference signs: 1 Pedal 2 reservoir 3 Piston plunger 4 Magnet armature 4a Stop of solenoid armature 4 Exciter winding 6 Solenoid yoke 7, 7a Pin 7, 7a Bolt AN1, AN2, AN3 Valve connections BK1, BK2 first and second brake circuit BP1, BP2 Separating valves DV Pressure supply device Fl, F2, F3 Filter FP Force due to hydraulic pressure H stroke of solenoid armature HV1 first hydraulic connection HV2 second hydraulic connection K1, K2, K3 valve chamber HLi Hydraulic lines MV, PD1, PD2 3/2-way valves PD15, PD25 Separating valve R1, R2 Working chambers of master cylinder SHZ/THZ Single or tandem master brake cylinder VF Valve spring VS1, VS11 first valve seat V52, VS22 second valve seat VSK11, VSK22 valve closing body WS Travel simulator MVs Shut-off valve

Claims

-13 -CLAIMS1. Hydraulic actuation system for a hydraulic system, in particular in the form of a braking system, comprising - at least one hydraulic circuit (BK) having at least one hydraulic consumer, in particular in the form of a hydraulically hydraulically actuated wheel brake, - having at least one pressure generating device (DV) comprising a pump, in particular in the form of a piston pump, which is used for the pressure control or regulation, in particular for pressure build-up and pressure (pauf, pab), in the at least one hydraulic circuit (BK1, BK2), and is used, characterized in that the pressure-generating device (DV) can be selectively connected to or disconnected from a reservoir (VB) by means of at least one controlled 3/2-way valve (PD1, PD2).
2. Hydraulic actuating system according to claim 1, characterized in that the pressure supply device (DV) has a piston pump, in particular with a plunger piston or double-stroke piston and at least one working chamber (KV, KH), and in that a first controlled 3/2-way valve (PD1) is assigned to the one first working chamber (KV), it being possible to connect either the first working chamber (KV) to a first hydraulic circuit (BK1) or to the reservoir (VB) by means of the first controlled 3/2-way valve (PD1).
3. Hydraulic actuating system according to claim 2, characterized in that the pressure generating device (DV) has a double-stroke piston (DHK) which separates the one first and the one second working chamber (KV, KH) from one another in a sealing manner, and in that a second controlled 3/2-way valve (PD2) is assigned to the one second working chamber (KH), it being possible by means of the second controlled 3/2-way valve (PD2) to connect either the second working chamber (KH) to a second hydraulic circuit (BK2) or to the reservoir (VB).
-14 - 4. Hydraulic actuating system according to claim 2, characterized in that a second controlled switching valve (PD25) is assigned to the one second working chamber (KR), which is a 2/2-way valve via which the second working chamber (KH) can be optionally connected to the second hydraulic circuit (BK2) or disconnected therefrom.
5. Hydraulic actuating system according to one of the claims 1 to 4, characterized in that a circuit separating valve (KTR) is provided for selective hydraulic connection or separation of the two hydraulic circuits (BK1, BK2), which serves in particular for opening or shutting off a hydraulic line (HL1-2) connecting the two hydraulic circuits (BK1, BK2) to one another.
6. Hydraulic actuation system according to claim 5, characterized in that a further circuit isolating valve (KTRs) is arranged in series with the circuit isolating valve (KTR) in the hydraulic line (HL1-2).
7. Hydraulic actuating system according to claim 1, characterized in that the pressure generating device (DV) has a double-stroke piston (DHK) which separates the one first and the one second working chamber (KV, KH) from one another in a sealing manner, and in that at least one of the two working chambers (KV, KH) of the pressure generating device (DV) is always connected to a reservoir (VB) by means of a controlled 3/2-way valve (PD1).
8. Hydraulic actuation system according to claim 7, characterized in that in an intermediate position of the controlled 3/2-way valve (PD1) both working chambers (KV, KH) of the pressure generating device (DV) are simultaneously connected to the reservoir (VB).
9. Hydraulic actuating system according to claim 7 or 8, characterised in that the pressure generating device (DV) has a double-stroke piston (DHK) which separates the two working chambers (KV, KH) from one another in a sealing manner, wherein a first hydraulic line (HL1) connects the first working chamber (KV) to a first valve connection (AN1) of the controlled 3/2-way valve (MV), and in that a second hydraulic line (HL2) -15 -connects the second working chamber (KV) to a second valve connection (AN2) of the controlled 3/2-way valve (PD1), and in that the third valve connection (AN3) of the controlled 3/2-way valve (PD1) is connected to the reservoir (VB) via a third hydraulic line (HL3).
10. Hydraulic actuating system according to claim 9, characterized in that, in a first valve position of the controlled 3/2-way valve (PD1), only its first valve connection (AN1) is in hydraulic connection with the third valve connection (AN3), and in that, in a second, in particular energized, valve position of the controlled 3/2-way valve (PD1), only its second valve connection (AN2) is in hydraulic connection with the third valve connection (AN3).
11. Hydraulic actuation system according to claim 10, characterised in that in the positions between the first and the second valve position all three valve ports (AN1, AN2, AN3) of the controlled 3/2-way valve (PD1) are hydraulically connected to each other.
12. Hydraulic actuation system according to one of the claims 7 to 11, characterised in that a first controlled switching valve (PD15) for the selective hydraulic connection of the first hydraulic line (HL1) or the second hydraulic line (HL2) is provided, the second working chamber (KH) to a first hydraulic circuit (BK1), in particular the first hydraulic line (HL1) is connected to the first hydraulic circuit (BK1) via a fourth hydraulic line (HL4), the first controlled switching valve (PD15) serving to selectively shut off or open the fourth hydraulic line (HL4).
13. A hydraulic actuation system according to any one of claims 7 to 12, characterised in that a second controlled switching valve (PD25) is provided for selectively hydraulically connecting the second hydraulic line (HL2) and the first working chamber (KV), respectively, to the second hydraulic line (HL2) and to the first working chamber (KV), respectively. the first working chamber (KV) to a second hydraulic circuit (BK2), in particular the second hydraulic line (HL2) is connected to the second hydraulic circuit (BK2) via a fifth hydraulic line (HL5), the second controlled switching valve (PD25) serving to selectively shut off or open -16 -the fifth hydraulic line (HL5).
14. Hydraulic actuation system according to one of the claims 12 or 13, characterised in that both hydraulic circuits (BK1, BK2) can be hydraulically connected to one another or separated from one another via a third controlled switching valve (KTV).
15. Hydraulic actuating system according to one of the preceding claims, characterised in that the pressure generating device (DV) can draw hydraulic medium into at least one working chamber (KV, KH) from a reservoir (VB) via at least one suction valve (SV1, 5V2).
16. Hydraulic actuating system according to one of the preceding claims, characterised in that a pressure or a piston position can be adjusted or set by means of the double-stroke piston (DHK) both in the forward stroke and in the return stroke.
17. Hydraulic actuating system according to one of the preceding claims, characterised in that a safety shut-off valve (MVs), in particular one which is open when de-energised, is arranged in the connecting line () which connects the valve (MV) to the reservoir (VB) and disconnects the hydraulic connection between the reservoir (VB) and the valve (MV), in particular in the event of malfunction and/or leakage of the valve (MV).
18. Brake system with a hydraulic actuation system according to one of the preceding claims, with at least one brake circuit (BK1, BK2) in which at least one hydraulically acting wheel brake is arranged in each case.